I've been trying CN for a couple of months. I'm asessing whether to switch from Evernote.

So far, I'm very impressed with CN's barebones simplicity. I think EN is slowly morphing from a notes app to a full text processing package such as Word or Framemaker. It will be called Nevernote or Pastnote or Exnote.

With EN I have far too many tags. Sometimes one tag is used for only a single note. So up till yesterday, I hadn't used tags with CN. That's because I wanted to have a few hundred notes before tagging with the minimum number of tags.

I notice that each time I create a new tag in CN, that tag is added to the left pane. That's fine.

But the new tag is also added in a new line below the current note. Is that a bug or a feature?

Is it possible to prevent these tags from using valuable lines in the grid?

Take a look at the settings page: Options > Notes List. There is a checkbox for "Display tags" that is on by default. If you uncheck it, then tags will not be displayed in the notes list. You can still see them in the Tags field when you open individual notes.